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Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Published on: August 9, 2011
An M29 Aminopeptidase from Listeria Monocytogenes Contributes to In Vitro Bacterial Growth but not to Intracellular
Xian Zhang1, Chiyu Guan1, Yi Hang1
1Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australian Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Zhejiang A&F University, Lin'an 311300, China.
Abstract:
Aminopeptidases that catalyze the removal of N-terminal residues from polypeptides or proteins are crucial for physiological processes. Here, we explore the biological functions of an M29 family aminopeptidase II from Listeria monocytogenes (LmAmpII). We show that LmAmpII contains a conserved catalytic motif (EEHYHD) that is essential for its enzymatic activity and LmAmpII has a substrate preference for arginine and leucine. Studies on biological roles indicate that LmAmpII is required for in vitro growth in a chemically defined medium for optimal growth of L. monocytogenes but is not required for bacterial intracellular infection in epithelial cells and macrophages, as well as cell-to-cell spreading in fibroblasts. Moreover, LmAmpII is found as dispensable for bacterial pathogenicity in mice. Taken together, we conclude that LmAmpII, an M29 family aminopeptidase, can efficiently hydrolyze a wide range of substrates and is required for in vitro bacterial growth, which lays a foundation for in-depth investigations of aminopeptidases as potential targets to defend Listeria infection.
Insights
The aminopeptidase II from Listeria monocytogenes (LmAmpII) is essential for bacterial growth in vitro. This enzyme, however, does not impact virulence or pathogenicity, suggesting it is not a viable target for anti-Listeria therapies.
Area of Science:
- Microbiology
- Enzymology
- Protein Biochemistry
Background:
- Aminopeptidases are vital enzymes involved in protein metabolism and cellular processes.
- The M29 family of aminopeptidases includes enzymes with diverse biological roles.
- Understanding specific aminopeptidases, like that from Listeria monocytogenes, is key to deciphering bacterial physiology.
Purpose of the Study:
- To characterize the enzymatic activity and biological functions of M29 family aminopeptidase II from Listeria monocytogenes (LmAmpII).
- To determine the role of LmAmpII in bacterial growth, infection, and pathogenicity.
- To evaluate LmAmpII as a potential therapeutic target against Listeria infections.
Main Methods:
- Enzymatic assays to determine substrate specificity and catalytic motif.
- In vitro growth studies in chemically defined media.
- Infection models using epithelial cells, macrophages, and fibroblasts.
- In vivo pathogenicity studies in a mouse model.
Main Results:
- LmAmpII possesses a conserved catalytic motif (EEHYHD) essential for its enzymatic activity.
- LmAmpII exhibits substrate preference for arginine and leucine.
- LmAmpII is required for optimal in vitro growth of Listeria monocytogenes.
- LmAmpII is dispensable for intracellular infection, cell-to-cell spread, and overall pathogenicity in mice.
Conclusions:
- LmAmpII is an active aminopeptidase crucial for in vitro Listeria monocytogenes growth.
- Despite its enzymatic activity, LmAmpII does not contribute to virulence or pathogenicity.
- Aminopeptidases may not be suitable targets for therapeutic intervention against Listeria infections.
